The previa brakes are larger than the GTS brakes, which will upset the brake balance even more. I've built this spreadsheet to analyse the braking system, you can use it to test out the balance and pedal effort that will be provided by your own components: MikesBrakes.xls. The rest of the brake design can be seen in the Brakes gallery.
On the front, the uprights are swapped from side to side to convert to a front steering rack, placing the disks at the rear of the wheels. The same has been done for the rear, which moves the brakes out of the way of the trailing arms.